Technological developments in material properties tailoring may require the use or application of a combination of two or more materials. In some instances, e.g., in the case of carbon/graphite-fiber-reinforced aluminum composites as "sandwiches," passivation of the layers or phases is necessary. This need for passivation of at least one of the layered materials is well known and widely reported.
Industrial high performance materials of the future are projected to make substantial utilization of aluminum and carbon-reinforced composites, and carbon fibers and fabrics theoretically have been described as providing desirable properties for high strength reinforcement. Among the desired properties are corrosion and high temperature resistance, low density, high tensile strength, and high modulus.
Reinforced components made from carbon graphite fibers have been observed to have limitations of undesirably low service ceiling temperatures, especially for applications using carbon graphite fibers exposed to the air or any oxidative environment. At temperatures as low as about 250.degree. C., carbon fibers are known to undergo thermally induced transformations which lead to degradation in strength. Reinforced components made from carbon graphite fibers, including carbon fiber/carbon fabric reinforced composites, can only be used up to a service ceiling temperature of about 400.degree. C. At temperatures approaching 400.degree. C. and above, the carbon fiber or fabric oxidizes, and the mechanical properties in the carbon composite degrade.
Accordingly, the passivation of the carbon is critically important. In a related manner, it is also critically important to passivate aluminum, especially in the case of sandwiches, to passivate the aluminum metal component. Such passivation treatment of aluminum or aluminum alloy metal protects the metal against galvanic or atmospheric corrosion to prevent chemical and oxidative attack from aggressive environments, particularly at elevated temperatures.
Technical efforts have been made to develop a thermal protection to increase limited service ceiling temperatures and to eliminate the erosion in properties which begins at about 250.degree. C. Currently, it is known to coat with inorganic coatings using chemical vapor deposition such as by SiO.sub.2 vapor deposition, or by physical vapor deposition, as by nickel vapor deposition. However, the vapor deposition processes are found to be expensive, and further are found to be capable of application only to limited shapes and sizes of fibers, layers, or substrates to be coated. Moreover, these vapor deposition methods would be incapable of uniformly coating fabric material, particularly in areas of interwoven fiber cross-over. The vapor deposition techniques also are known to have residual porosity, which porosity would provide centers of attack by the oxidative agents.
Brown et al., Canadian Patent No. 662,670, disclose novel organopolysiloxanes. The Brown et al. siloxy units are linearly arranged using alkaline rearrangement catalyst for producing a white solid which then is dissolved in benzene. The polymer obtained is in the form of long white fibers. The solid is insoluble in methanol.
Brown et al. call for a precopolymer of either diphenylsiloxy or siloxy containing alkyl, alkenyl, or cyanoalkyl radicals to produce solid (intrinsic viscosity in benzene), high molecular weight organopolysiloxanes having aryl radicals, but which also can have, alkyl and alkenyl radicals.
Japanese patent application JO 1092-224-A by Mitsubishi Denki in its Abstract discloses phenylsilicone ladder polymer useful as interlayer insulation film of a semiconductor device.
In the search for high performance materials, considerable interest has been focused on carbon fibers and fabrics. The term "carbon" is used herein in its generic sense and includes graphite as well as amorphous carbon. Graphite fibers are defined herein as fibers which consist essentially of carbon and have a permanent x-ray diffraction pattern characteristic of graphite. Amorphous carbon fibers, on the other hand, are defined as fibers in which the bulk of the fiber weight can be attributed to carbon and which exhibit an essentially amorphous x-ray diffraction pattern. Graphite fibers generally have a higher Young's modulus than do amorphous carbon fibers and in addition are more electrically and thermally conductive. Carbon fabrics are sheet-like products formed from interwoven carbon fibers.
Aluminum sheet material is used in conventional reflector systems of electric lighting fixtures. Such specular sheet material typically has a total reflectance of about 87% or more. There still remains a need to improve the total reflectance of specular aluminum sheet material to increase efficiency of lighting fixtures and to reduce consumption of electricity.
Pankin, U.S. Pat. No. 4,562,517, discloses a method for improving the efficiency of lighting fixtures by providing reflectors coated with a very thin film of silver covered by a polymer. Such reflectors perform adequately for a while, but they are subject to delamination over long periods of time.
Ohno et al., U.S. Pat. No. 4,348,463, disclose a reflector of a metal substrate, a resin layer on the substrate, a light reflective metal over the resin layer, and a layer of ceramic over the metal layer. The Ohno et al. resin layer can include alkyl groups, and the number of functional groups in polymerizable groups is 2-3, i.e., X, Y, Z are 2-3.
It is an object of the present invention to produce a polymer-coated carbon, metal, or ceramic layer or substrate having enhanced thermal protection and oxidative stability.
It is a further object of the present invention to produce a polymer-coated carbon, metal, or ceramic layer or substrate, or a resultant carbon-reinforced composite produced therefrom, in an economical and efficient manner and method, including for the application of the polymer coating.
It is another object of the present invention to provide a carbon, metal, or ceramic layer or substrate coated efficiently by a polymer coating process scaled up for any shape or size of carbon, metal, or ceramic layer or substrate to be coated.
It is an object of the present invention to provide a method for synthesizing coatings which confer enhanced thermal protection and oxidative stability to carbon, aluminum, iron, steel, silicon dioxide, and other metal and ceramic layers or substrates.
It is another object of the present invention to provide a product and method for providing thermal protection and oxidative stability to carbon, metal, or ceramic layers and substrates without requiring high initial capital costs for producing the product or method.
It is a further object of the present invention to provide for coating carbon fibers or fabrics or to form a polymer-coated carbon or graphite fiber or fabric, or a resultant carbon-reinforced composite formed therefrom, having thermal protection and oxidative stability at temperatures higher than about 400.degree. C.
It is an object of the present invention to provide a method for improving the total reflectance of aluminum sheet material.
A related objective of the invention is to provide a gel film coating for aluminum sheet material that will improve the reflectivity of a reflector layer overlying the gel film.
These and other objects of the present invention will become apparent from the detailed description which follows.